| Message ID | CAH6eHdQPpktHs6HR8NRCk955U_PmG0xxrBjFNwHaTSTzaWZN-A@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
Indeed, default constructor and copy constructor shall not be noexcept qualified. IMO we should be able to make move constructor noexcept by using a special allocator for the underlying unordered_map that would allow to replace an entry with an other one without requiring a deallocate/allocate. It would be the same kind of allocator keeping a released instance in cache that you already talk about to enhance std::deque behavior especially when used in a std::queue. For 4.9 we could consider that this test is not supported in profile mode and I will work on it for next version. François On 01/26/2014 11:38 AM, Jonathan Wakely wrote: > On 26 January 2014 09:43, François Dumont wrote: >> Hi >> >> This is a patch to fix PR 55033 in profile mode. Like in debug mode it >> was missing noexcept qualifier on move constructor. > But don't those functions allocate memory? So they can throw. > > I agree we want the move constructor to be noexcept anyway, and maybe > the default constructor, but why would we want to lie about the copy > constructor? > > I have this patch in my tree that I'm trying to decide whether it > should be committed, but if we make the change we should have a > comment like this: > > --- a/libstdc++-v3/include/profile/unordered_base.h > +++ b/libstdc++-v3/include/profile/unordered_base.h > @@ -160,9 +160,14 @@ namespace __profile > __profcxx_hashtable_construct(&__uc, __uc.bucket_count()); > __profcxx_hashtable_construct2(&__uc); > } > + > _Unordered_profile(const _Unordered_profile&) > : _Unordered_profile() { } > - _Unordered_profile(_Unordered_profile&&) > + > + // This might actually throw, but for consistency with normal mode > + // unordered containers we want the noexcept specification, and will > + // std::terminate() if an exception is thrown. > + _Unordered_profile(_Unordered_profile&&) noexcept > : _Unordered_profile() { } > > ~_Unordered_profile() noexcept >
--- a/libstdc++-v3/include/profile/unordered_base.h +++ b/libstdc++-v3/include/profile/unordered_base.h @@ -160,9 +160,14 @@ namespace __profile __profcxx_hashtable_construct(&__uc, __uc.bucket_count()); __profcxx_hashtable_construct2(&__uc); } + _Unordered_profile(const _Unordered_profile&) : _Unordered_profile() { } - _Unordered_profile(_Unordered_profile&&) + + // This might actually throw, but for consistency with normal mode + // unordered containers we want the noexcept specification, and will + // std::terminate() if an exception is thrown. + _Unordered_profile(_Unordered_profile&&) noexcept : _Unordered_profile() { } ~_Unordered_profile() noexcept